Ok, so I have this Web site project under VS 2010, Net 3.5 and Infragistics 10.2. I have been using WebDataGrid in the project but I need some specific functionality that can only be provided by the older UltraWebGrid. So, I added the UltraWebGrid dll to the Project and to the web config to include the control. I verified that Web.UI.Shared was there too and with the same version number.  Unfortunately, adding the control to the aspx page renders a compilation error:

 The type or namespace name 'UltraWebGrid' does not exist in the namespace 'Infragistics.Web.UI' (are you missing an assembly reference?)

It does not seems to me I am missing any reference; I am also adding this to the aspx file:

<%@ Register Assembly="Infragistics35.WebUI.UltraWebGrid.v10.2, Version=10.2.20102.1011, Culture=neutral, PublicKeyToken=7DD5C3163F2CD0CB"
    Namespace="Infragistics.Web.UI.UltraWebGrid" TagPrefix="ig" %>

And the following piece of code is not recognized:

       <ig:UltraWebGrid ID="UltraWebGrid1" runat="server"  >

         </ig:UltraWebGrid>

Also, the error points to the following piece of code with the underlined word as the offending part:

        protected global::Infragistics.Web.UI.UltraWebGrid.UltraWebGrid UltraWebGrid1;

Thanks for your help!